From previous results of our studies, it is clear that gap junctional communication compartments exist in the Drosophila wing imaginal disk and they appear to coincide with the positions of lineage compartments. In light of these observations and the fact that lineage compartments are thought to play a fundamental role in organizing development in insects, we propose that communication compartments may also play an important role in regulating patterning events in development. To further examine this possibility, in this proposal we will characterize the gap junctional communication properties of cells in the Drosophila embryo and larval hypoderm. The specific aim is to detemrine if there are communication compartments present in the insect hypoderm early in development, before and after the time of segmentation, and whether the borders of such compartments coincide with segmental boundaries. Based on previous observations, we expect that the segment borders will coincide with communication restriction borders and moreover, if cell-cell communication plays a role in organizing the overall body plan of insects, it is likely that there will be alterations in the pattern of cell-cell communication in step with the specific pattern perturbation in each mutant. Microelectrode impalements will be used to monitor ionic and dye coupling and we consider it likely that communications compartments will be detected, some or all of which will have borders that coincide with the borders of segments. To document the three dimensional distribution of the injected dye, lucifer yellow injected specimen will be further analyzed histologically in thick sections. The presence of cytoplasmic bridges will also be monitored by injecting horse radish peroxidase and histochemically localizing the injected enzyme. Additional experiments will be caried out to examine the possible structural basis for the formation of communication restrictions. These experiments will involve injecting fluorescently labeled peptides of various sizes to determine whether there is an alteration in gap junction permeability at a restriction boundary. It is hoped that these studies together will provide insights into the role of gap junctions in pattern formation.